1. Technical Field
The present invention relates to an image forming optical element that forms an erected image of an object, an image forming optical array, and an image reading device that reads an image of an object using the image forming optical element.
2. Related Art
In an image scanner, a facsimile, a copier, a financial terminal device, a contact image sensor module (hereinafter, referred to as “CIS module”) is used as an image reading device. The CIS module has a light source unit that irradiates a reading target with light, an image forming optical unit that forms a erection equal-magnification image of the reading target, and an optical sensor that reads the erection equal-magnification image formed in the image forming optical unit, and disposition relationship between the image forming optical unit and the optical sensor is fixed. This is one of main factors decreasing the degree of freedom in disposition of the optical sensor. For example, as described in JP-A-2000-66134, it is proposed that a reflection member is disposed on an image forming side of a roof prism lens array, an image forming side optical axis is bent such that a positional range in which the optical sensor can be disposed drastically spreads.
However, in the roof prism lens array, an object side lens face and an image forming side lens face are perpendicularly disposed, a structure in which a ridge is disposed to be 45° with respect to a plane including the optical axes of two lenses is employed, and thus it is difficult to avoid complication of the image forming optical unit. To satisfactorily obtain the erection image of the reading target, it is necessary to determine the position of the ridge with high precision and to adjust the relative positional relationship with the reflection member with high precision.